assume cs:code, ds:data

data segment
    db 'ibm             '
    db 'dec             '
    db 'dos             '
    db 'vax             '
data ends

stack segment stack
    dw 0, 0, 0, 0, 0, 0, 0, 0
stack ends

code segment
start:
    mov ax, data
    mov ds, ax
    mov ax, stack
    mov ss, ax
    mov sp, 16

    mov cx, 4
    mov bx, 0
list:
    push cx
    mov si, 0
    mov cx, 3

roll:
    mov al, ds:[bx+si]
    and al, 11011111B
    mov ds:[bx+si], al
    inc si
    loop roll

    add bx, 16
    pop cx

    loop list

    mov ax, 4c00H
    int 21H
code ends

end start